Background: Access to antiretroviral therapy has dramatically expanded in Africa in recent years, but there are no
validated approaches to measure treatment adherence in these settings.

Methods: In 16 health facilities, we observed a retrospective cohort of patients initiating antiretroviral therapy. We
constructed eight indicators of adherence and visit attendance during the first 18 months of treatment from data
in clinic and pharmacy records and attendance logs. We measured the correlation among these measures and
assessed how well each predicted changes in weight and CD4 count.

Results: We followed 488 patients; 63.5% had 100% coverage of medicines during follow-up; 2.7% experienced a
30-day gap in treatment; 72.6% self-reported perfect adherence in all clinic visits; and 19.9% missed multiple clinic
visits. After six months of treatment, mean weight gain was 3.9 kg and mean increase in CD4 count was 138.1
cells/mm3.
Dispensing-based adherence, self-reported adherence, and consistent visit attendance were highly correlated. The
first two types of adherence measure predicted gains in weight and CD4 count; consistent visit attendance was
associated only with weight gain.

Conclusions: This study demonstrates that routine data in African health facilities can be used to monitor
antiretroviral adherence at the patient and system level.